This invention pertains generally to a method of fabricating an MRAM structure, and more particularly, to an MRAM structure that has the pinned layer recessed within a trench with an upper magnetic layer positioned over it.
Integrated circuit designers have always sought the ideal semiconductor memory: a device that is randomly accessible, can be written or read very quickly, is non-volatile, but indefinitely alterable, and consumes little power. Magnetoresistive random access memory (MRAM) technology has been increasingly viewed as offering all these advantages.
A magnetic memory element has a structure that includes magnetic layers separated by a non-magnetic layer. Information can be written and read as a xe2x80x9c1xe2x80x9d or a xe2x80x9c0xe2x80x9d as directions of magnetization vectors in these magnetic layers causing resistance variations. Magnetic vectors in one magnetic layer are magnetically fixed or pinned, while the magnetic vectors of the other magnetic layer are not fixed so that the magnetization direction is free to switch. In response to these shifting states, the magnetic memory element represents two different resistances or potentials, which are read by the memory circuit as either a xe2x80x9c1xe2x80x9d or a xe2x80x9c0.xe2x80x9d It is the detection of these resistance or potential differences that allows the MRAM to read and write information.
It would be desirable to be able to fabricate higher density MRAM memory devices with increased precision, and with a reduced number of simplified steps. It would be desirable to be able to form one or more integrated MRAM devices so that accurate placement of the top magnetic layer over the bottom pinned magnetic layer can be assured. A self-aligned process would serve this purpose. It would be an advantage if such a process were easily repeatable so as to allow the fabrication of a plurality of layers of MRAM device integration.
This invention pertains to a method of fabricating an MRAM structure and the resulting structure. The MRAM structure of the invention has the pinned layer recessed within a trench with an upper unpinned magnetic layer positioned over it. The method of fabrication utilizes a spacer placed within an etched insulator opening to reduce the opening size. The upper magnetic layer of the MRAM stack structure is formed within the smaller size region defined by spacers, thereby allowing for accurate placement and self-alignment of the upper magnetic layer over the underlying pinned magnetic layer. This process is repeatable to form multiple MRAM device layers for heightened levels of vertical integration.
These and other feature and advantages of the invention will be more clearly understood from the following detailed description, which is provided with reference to the accompanying drawings.